1-[2-(4-amino-1-piperidinyl)ethyl]-8-ethyl-7-fluoro-1,5-naphthyridin-2(1H)-one (0.117 g, 0.368 mmol) and 6,7-dihydro[1,4]dioxino[2,3-c]pyridazine-3-carbaldehyde (0.061 g, 0.368 mmol) were dissolved in CHCl3 (2 ml) and MeOH (0.2 ml) at rt under argon. NaBH(OAc)3 (0.234 g, 1.10 mmol) was added and the reaction was allowed to stir at rt for 16 h. After which it was purified by chromatography on silica gel using a 0-30% MeOH in DCM gradient to give the free base of the title compound as a clear oil (0.045 g, 26%).
